I agree with the no gain from synthetic oil idea. From what I know about oil (which isn't a whole lot) the intermolecular shearing forces of conventional oil are actually less than the synthetic, and therefore actually reduce friction. Theoretically going with low viscosity conventional oil would be the best for friction reduction. Having said that however, I change my oil with OEM recommended weight synthetic every 3000 miles. It's not worth the risk of experimenting with oil in my opinion.

I don't agree on that, because in general the synthetic oils have a lower viscosity (0W30 e.g.) and this helps saving fuel and protects your engine better for two major reasons:
1) lubrication starts faster (better engine protection)
2) less pumping losses for the oilpump
Difference can be up to 2%, depending on driving conditions (colder climate/short distances, => bigger advantage with synthetic).
By the way: changing oil every 3000 miles... ?? My father did this with his first car back in the seventies, but technologie improved since.

I think we had a discussion about oil a while back. several of us couldn't remember ever knowing of a vehicle that had died because of oil change interval discrepencies (as long as it had oil in it)

I have a really strange oil changing ritual in my house. change oil every 3mos/3k mi and filter every 6mos/6k mi. I also used the pennzoil (dino juice). it is more of habbit than anything but it seems to work for me. I do use the mobile 1 (or similar) filter.

some people have played with using 0w-XX oil but I haven't seen too many people boasting of gains from that.

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What I mean is this: if you're car requires 5w 30 for example, you can get either conventional or synthetic. Conventional oil has less intermolecular forces and therefore will result in less friction. Keep in mind that metal should never touch in your engine, so the friction comes from vistosity of the oil and ther intermolecular forces. You shouldn't go outside of what the OEM says to run, so if you want less friction conventional will have a marginal advantage. Let me stress MARGINAL.

When I change my oil at 3000 miles it's quite dark, so I'll keep changing it around there. I know lots of people go much longer, but my car is American made. I just can't justify going longer when I know it's already on its way to being burnt at 3000. I realize that dark oil doesn't automatically mean that it's used up, but I really can't risk damaging my engine when I depend so heavily on my vehicle every day.

On a side note, the oil you buy from the parts store that says it's synthetic actually isn't. Mobil 1 lost a lawsuit in regaurds to this. It's all very interesting, Google it.

Also of interest, there is a company called Luberzol that supplies oil to practically all the oil distribution companies. All the oil you buy comes from the same place essentially, just with different amounts of additives etc. Buying oil is like buying mixed drinks from different bars haha.

I remember oil changes when I was a kid working on our 1980 Bonneville with my dad. If I remember correctly the manual stated a 7,500 mile oil change, but he did 5,000 for simplicity. On my truck, the manual calls for a 7,500 mile interval. I use synthetic, and still adhere to dad's 5,000 mile schedule. I'm sure I could push it to 10,000 miles, but I'm happy with 5,000. By the time I'm a quart low I need to change it anyway. My oil never turns black, it looks like medium to dark honey coming out.

I don't agree on that, because in general the synthetic oils have a lower viscosity (0W30 e.g.)

The viscosity measurement (like 0W30) is just that - a measurement. So, if one oil inherently is less viscous than another, it will be rated as lower viscosity.

The ratings are somewhat general but I don't think there's a pattern. A conventional or synthetic oil rated 5W30 may be randomly less or more viscous than any other, but all 5W30 oils should be heavier viscosity than all 0W20 oils.

Edit: If it wasn't that way, car manufacturers would have sued oil manufacturers and the API. They expect consistency from oil ratings and design their engines based on those ratings.

Quote:

Originally Posted by BEEF

I think we had a discussion about oil a while back. several of us couldn't remember ever knowing of a vehicle that had died because of oil change interval discrepencies (as long as it had oil in it)

I consistently challenge people to post their experiences regarding oil change intervals, oil quality choices, and oil-related engine failures. If anyone reading this has had such a failure, please post about it!

The reality is that almost all cars go to the junkyard having never suffered a failure that can be blamed on oil choice or oil change interval. Few people ever manage to post data showing anythine else, even though we all know plenty of people who do not maintain as well as the oil companies' marketing departments say we should.

Quote:

Originally Posted by drifttec101

On a side note, the oil you buy from the parts store that says it's synthetic actually isn't. Mobil 1 lost a lawsuit in regaurds to this. It's all very interesting, Google it.

The lawsuit was about whether it can be called "Synthetic" if it is originally from dinosaur juice but was thoroughly processed, or if it must be manufactured in a lab from something (PAO base stock) other than dinosaur juice. The end result was that oil manufactured from dinosaur juice can be called synthetic if it has the quality and consistency of PAO-based oils.http://motorcycleinfo.calsci.com/Oils1.html

Quote:

In the late 1990s, Castrol started selling an oil made from Group III base oil and called it SynTec Full Synthetic. Mobil sued Castrol, asserting that this oil was not synthetic, but simply a highly refined petroleum oil, and therefore it was false advertising to call it synthetic. In 1999, Mobil lost their lawsuit. It was decided that the word "synthetic" was a marketing term and referred to properties, not to production methods or ingredients. Castrol continues to make SynTec out of Group III base oils, that is highly purified mineral oil with most all of the cockroach bits removed.

Shortly after Mobil lost their lawsuit, most oil companies started reformulating their synthetic oils to use Group III base stocks instead of PAOs or diester stocks as their primary component. Most of the "synthetic oil" you can buy today is actually mostly made of this highly-distilled and purified dino-juice called Group III oil. Group III base oils cost about half as much as the synthetics. By using a blend of mostly Group III oils and a smaller amount of "true" synthetics, the oil companies can produce a product that has nearly the same properties as the "true" synthetics, and nearly the same cost as the Group III oil. The much more expensive traditional synthetics are now available in their pure forms only in more expensive and harder to obtain oils. To the best of my knowledge, Delvac-1, AMSOil, Redline, and Motul 5100 are the only oils made from pure traditional synthetics.

my dad once bragged about not chainging his oil for over a year (maybe it was almost a year). I was too young to really care. he sold that truck to my step-grandfather who still drives it with who knows how many miles on it. it was a B series mazda truck (basically a ranger).

dad got rid of it because it would stutter in 5th gear under high loads (pulling a boat). ironically enough, changing the plugs seemed to fix most of that. my uncle did that for my step-grandfather after he bought it. dad was ready for a new vehicle anyway.

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I once knew a guy in the early 90's that had a Chevy K1500 that he bragged never had the oil changed, or vehicle washed since it was new. It looked like hell, but still ran decently. Last I saw him he had well over 150,000 miles on it.

If you really want 100% synthetic oil you need to buy pure synthetic racing oil. The problem with that is most racing oil has the molecule ZDDP (zinc...). The zinc is great for your engine, but not for emissions testing. It's banned from being in parts store oil. So even the really good parts store oil like Royal Purple isn't all that great. http://www.bradpennracing.com/ That is the oil I use in my race car. All the engine builders in my area recommend nothing but that oil. They do make lighter weight oil like 0w 30 that would work in most of our engines. It is a bit pricey though.